Wind turbine blades, and parts thereof, are often manufactured from layers of resin-preimpregnated fibres, called prepregs, which are arranged on a moulding surface and subjected to vacuum and heat to cause a melting or softening of the resin followed by a curing thereof.
A drawback related to the use of prepregs is that the material is often delivered rolled-up, and the shape retention of the material may cause problems during the lay-up process because of wrinkles of the fibres being formed. This is especially the case for large product thicknesses, where wrinkles in lower layers can worsen the distortions in upper layers even further than what is caused by shape retention of the individual layers alone.
Furthermore, the prepregs have only limited sidewise stability, and care must be taken to avoid misalignment of the fibres during lay-up. The handling of prepregs can be particularly difficult when prepregs of large size are cut to the desired shape at one working surface and subsequently has to be moved to and arranged on the moulding surface.
Another drawback is that the curing is an exothermic process and therefore may result in disadvantageous built-in thermal stresses and deformations in the finished product, especially for products having a large thickness. A further disadvantage related to the exothermic curing process is that the heat may result in degradation of material which cannot withstand the actual temperatures which arise during the curing process.
Hence, an improved manufacturing method would be advantageous, and in particular a manufacturing method overcoming the above mentioned disadvantages would be advantageous.